Guo-Ding Zhou

Passivation model of 316 stainless steel in simulated cooling water and the effect of sulfide on the passive film

Through the measurement and analysis of electrochemical impedance spectroscopy (EIS) data from the 316 stainless steel/simulated cooling water system, among the four selected passivation models, the equivalent circuit of Model D is most consistent with the conditions of this system. In this model, the charge-transfer resistance R1 is relatively small at the beginning of the immersion. When the immersion time increases, the values of R1 and Y01 stabilize. Over the time period of the immersion, the film resistance R2 increases while the value of Y02 decreases continuously, indicating that the passive film is getting thicker and more compact. With the addition of sulfide, R2 decreases rapidly. The polarization curve shows that the passivity current of the stainless steel increases with addition of the sulfide. The Mott–Schottky plots indicate that as the sulfide concentration increases, the slope of the straight segment which reflects the properties of p-type semiconductor (chromium oxide) decreases or even almost disappears. The slope of the straight segment which reflects the properties of n-type semiconductor (iron oxide) also decreases, and the acceptor density NA and the donor density ND increase to a certain extent. This shows that the sulfide changes the composition and structure of the passive film of the stainless steel and thereby decreases the corrosion resistance of the film.

Electrochemical and photoelectrochemical study of the self‐assembled monolayer phytic acid on cupronickel B30

Purpose – The purpose of this paper is to investigate the self‐assembled monolayers (SAMs) of phytic acid on cupronickel B30 surface of anticorrosion and inhibiting mechanisms.Design/methodology/approach – Electrochemical and photocurrent response methods were performed to determine the effect of phytic acid SAMs on cupronickel B30.Findings – The results indicated that phytic acid was liable to interact with B30 as a result of formation of complexes on B30 surface for anti‐rust and anti‐corrosion. The SAMs changed the structure of the electrochemical double layer and made the value of double layer capacitance decrease significantly. The B30 electrode showed p‐type photoresponse, which came from Cu2O layer on its surface. The photoresponse decreased greatly due to the SAMs of phytic acid as the corrosion resisting property was enhanced. This finding was in good agreement with the results obtained from EIS and polarization curves. Adsorption of phytic acid was found to follow the Langmuir adsorption isother...

Photoelectrochemical study on the complex of PASP and tungstate as inhibitors of cupronickel B10's corrosion

Photoelectrochemical and AC impedance measurements were conducted to study the effects of environment-friendly inhibitors poly-aspartate(PASP), Na2WO4 and their complex on the corrosion of cupronickel B10 in a borax-buffer solution. The photoelectrochemical measurement results indicated that PASP or Na2WO4 increased the p-type photocurrent which came from the Cu2O layer on the B10 surface. It showed that the inhibitors increased the thickness of the Cu2O layer and decreased the corrosion speed. The optimal concentrations of PASP and Na2WO4 was 3 and 5 mg·L-1, respectively. Na2WO4 increased photocurrent more than mono PASP did. Combined use of PASP and Na2WO4 in a total concentration of 5 mg·L-1, when the mass ratio(PASP: Na2WO4) was 1∶1 or 1∶3, increased the photocurrent more than their individual use did. The bigger the photocurrent was, the better the inhibition efficiency was. When the mass ratio (PASP: Na2WO4) was 3∶1, the combined use increased photocurrent less than their individual use did, the inhibition effect decreased. AC impedance measurement results were well agreed to the photo-electrochemical results.